Parallel parking is a method of parking a vehicle in line with other parked cars. Cars parked in parallel are in one line, parallel to the curb, with the front bumper of each car facing the back bumper of an adjacent one. Since parallel parking is parallel to the curb of a road, roads that facilitate said parking have an extra lane or a large shoulder for parked cars. It is also employed anytime perpendicular parking facilities are not available or hard to come by commonly, that's in large metropolitan areas where there is a high density of vehicles and few (or restricted) accommodations such as parking garages.
Parallel parking is considered by many to be one of the hardest skills for new drivers to learn. Following are the typical steps for performing a parallel parking:                Signal into the space.        Ensure that the desired parking space is about 2 meters longer than the vehicle's length.        Line up the vehicle beside the vehicle in front of the parking space.        Turn the steering wheel one turn towards the curb and put the vehicle into reverse.        Back up the vehicle so that the rear bumper is first to enter the parking space.        Once the vehicle is at 45° to the parking spot, slow down and turn the steering wheel all the way, to the road side.        Continue backing up until the vehicle is parallel with the curb.        Gradually turn the steering wheel towards the curb to curve the vehicle into a straight position.        Brake once the vehicle occupies the middle of the parking space.        Make sure that the vehicle is not parked too far from the curb.        
Recognizing the problem of performing an accurate parallel parking some car manufacturers are trying to automate the parking process. For example, one car manufacturer recently disclosed its automated parking system. This system relies on a built-in computer, steering sensor and a tiny camera in the car's rear and works like this:
A dashboard display shows the image taken by the camera. When you near a parking space and shift into reverse, computerized lines pop up on the display, along with arrows pointing up, down, left and right. Using the arrows, you move the lines around until they define exactly where you want the car to be parked. Then you push the “set” button on the display. Keep your foot lightly on the brake pedal, and the car will start backing up, the steering wheel responding to an invisible hand. Voila, the car will park itself in the spot you've chosen with the arrows.
While easy to use, the above automated system is expensive and difficult to implement during the manufacturing process.
Other solutions include the one described in U.S. Pat. No. 6,163,253 entitled “Method and Apparatus for Guided Parking of a Vehicle Using Ultrasonic Position Detection.” The '253 Patent discloses a system having a sensing and indicating device mounted at a fixed location and using transmitted and reflected acoustic or electrical energy to determine the distance between the sensor and an approaching vehicle. The sensor provides visual and/or audible indication of the distance between the vehicle and the sensor. The driver of the vehicle uses that displayed or audible information to locate the vehicle within a defined space or envelope, e.g., within a garage. The sensor and indicator may also be located laterally with respect to the vehicle so that the distance between the vehicle side and the sensor can be determined whereby the vehicle can be located laterally within the defined space or envelope.
Similarly to the system described above, the system of the '253 Patent is expensive is difficult to implement.
Accordingly, there is a need in the art for a structure providing a more convenient and safe way to correctly and accurately perform parallel parking.